[asterisk-users] What's the story with X10*P FXO cards?

[Rich Adamson]

>     It looks like the X101P clones I bought from eBay are dogs, so I'll 
> look into buying some FXO-SIP box instead. Hopefully, I won't have the 
> same problems with static, or caller ID and call termination not being 
> detected.
> 
> Still, considering the number of people having similar problems with 
> those cards, I was wondering what the problem is. Is it because the 
> hardware, no matter what is advertised, is actually not identical from 
> card to card so the zaptel driver doesn't work reliably unless they are 
> among the few remaining authentic cards made by Digium before it stopped 
> manufacturing them? Because they're actually voice softmodems, and 
> hence, very sensitive to the  computers in which they're installed 
> (voltage on the PCI slot, sharing IRQ's, etc.)? Other reasons?

The X100P-style cards were never manufactured by Digium; they were 
simply analog modem cards that happened to use integrated circuits with 
some voice encoding/decoding functionality. The card was manufactured 
overseas using a chipset from Silicon Labs, and were fairly popular back 
in the pre-broadband analog-modem days. Digium wrote the asterisk 
drivers to take advantage of the functionality within the chipset.

The Silicon Labs chipset used on the card was designed to meet US 
Telephone standards, and several competing analog modem manufactures 
designed their cards using Motorola, Intel, and/or other chipsets. Each 
chipset has its own unique driver requirements in terms of initializing 
the chips, moving data, timing, etc. Also keep in mind the card designs 
were mostly completed back in the days of PCI v1 standards.

Some of the cards sold on Ebay are those that use the Silicon Labs 
chipsets while others are obviously based on the Motorola chipset. The 
two are not interchangeable without modifying the asterisk drivers.

As mentioned, the Silicon Labs chipset used on the card were 
manufactured to US telephone standards (eg, 600 ohm impedance). Other 
countries have different standards (guessing, maybe 30-to-50 different 
telephony standards), and attempting to use the x100p in those 
environments represents electrical mismatches resulting in echo, no 
callerid support, and many other objectionable or non-working conditions 
(depending upon exactly which country you were in).

Are some of the Ebay ad's misrepresented? Probably.

You're likely to become just about as frustrated with the fxo-sip 
gateway boxes on the market. Expensive ones have excellent echo 
cancellation while the cheaper ones are rather poor (or unusable). Some 
will accept incoming pstn calls while others basically only support 
outgoing calls (intended for certain failed conditions). Some are 
targeted for the US market (telephony standards) while others support a 
larger subset. Some work well on long pstn loops while lots of them 
don't work very well at all.